Welded cast-iron article and method



April 28, 1931. I PHELPS 1,802,778

WELDED CAST IRON ARTICLE AND METHOD Filed Jan. 2. 1929 Evwanboz GEORGE/i 1 /151. F51

. Patented Apr. 28 1931 UNITED STATES PATENT OFFICE" v f GEORGE E. rianrrs, or WAREHOUSE POINT, CONNECTICUT, AssIeNoR, BY MEsNE s sIeNMEN'rs, TO METROPOLITAN ENGINEERING COMPANY, a CORPORATION or NEW YORK r i I WELDED CAST-IRON ARTICLE ANnJuE'rHoD Application filed January 2, 1929. Seriallto. 329,904.

Cast iron containsa high percentage of carbon in various molecular and structural dispositions. The gray cast irons contain a considerable amount of graphite. Sometimes the whole of the carbon is in this graphitic condition, sometimes part of it is chemically combined with the iron. The graphite is in numerous irregular and generally elongated and curved plates imbedded in the metal ma-,

l0 trix of ferrite or iron ompounds, which plates breakup the continuity of the mass so effectively as to destroy the ductility and malleability of the otherwise'ductile and malleable matrix. v

Malleable cast iron is made by annealing hard castings (in which all of the carbon is combined chemically with the iron) By reason of the extreme slowness of the annealing operation, a matter of days generally, the

graphite is segregated from theferrite or from the combined iron and carbon in small rounded isolated particles, which do not materially reduce the ductility and malleability of the matrix. a I i The present invention is directed to theuse of such-gray cast iron and malleable cast iron and similar products containing substantial amounts of graphite.

The welding of such cast iron has presented difliculties in preserving the molecular struc ture so that the only methods in general ap-.

plication have been. gas and arc welding, which involve the depositing of molten metal (usually of a different composition). along the joint. I have found that cast iron parts of thedescribed composition can be united by resistance welding by using the Murray (Re- 1 issue Patent No. 15,466, October 10, 1922) and similar high-speed processes in which the parts are pressed together whilea current is passed across the oint of extremely high density or amperage per square inch for a very brief period of time. Apparently because of the speed of the operat1on, there is no great solution of the graphite such as would convert. the metal to graphite-free white cast iron; as would result from an ordinary-resistance welding operation. White cast iron is practically graphite-free and is a hard brittle metal, little bene detected as a cut was being taken in a lathe across the weld zone and contmued on across metal unafiected by the heat of welding. The weld was furthermore rendered practically identical with the unafiected metal in strength and brittleness, as far as these properties can be detected by rough tests, by this short anneal at ordinary annealing temperatures.

The effectiveness of these short anneals at 1450 degrees F. indicated strongly that a great majority of the graphite contained in the original gray iron had not been dissolved in the metallic matrix during the very brief time during which the metal was at or near its melting point in process of welding, but had rather remained as graphite mechanically entrapped, throughout the welding. if

this were the case the matrix would correspond in hardness to a high carbon steel drastically quenched from a high temperature, and this hardness would be easily removed by a simple short anneal similar to that which would soften a quenched high carbon steel. This, of course, is in agreement with the experimental results previously referred to.

A rough determination by microscopic examination of such welds indicates that the metal in the welded zone contains an amount of graphite nearly equal to that contained in the original metal. The graphite in the weld appears in a different arrangement, the or ginal flakes having been broken up into smaller fragments by the pressure and take-up of the welding operation.

. Similar circumstances have been found in welding malleable castings. Using the Murray and similar methods,.the parts can be welded and can be restored to their original .mallea-ble condition orapproz zimately so at were retained to a substantial extent in spite of the welding operation.

The annealed welds were found to be as strong as the rest of the metal and were not seriously brittle, and the hardness was not suificiently greater than in the parent metal to prevent machining or cutting.

In summary then we find that gray cast iron, or malleable cast iron, when welded by the Murray process results in welds which are hard and brittle but which by a simple anneal at low temperatures and for a short period of time can have their original good properties restored.

This makes possible theme of butt welding in a new field-'malleable castingswhere the advantage of making a finished piece by welding together two or more castings may in many cases simplify the original casting and malleableizing operations to such an extent as to result in very considerable savings 'in cost. .Furthermore .certain shapes which it was fornierly impractical to cast and malleableize may now be handled economically,

For example the attached drawing shows an article made of two plates 1 connected by a web 2. In casting such an'article the web shrinks-in cooling and is apt to break away from the end plates. The three parts, however, may be se arately cast and malleableized and then method along the joints 3.

utt-welded by the present 7 Various modifications may be made by those skilled in the art without departure from the invention as defined in the following claims.

Claims:

- 1. An article consisting of parts of gray cast iron or malleable cast iron welded together without the addition of othermetal, the metal in the weld containing approximately the same amount of graphite as the metal beyond the welded zone.

2. The method of uniting parts of gray cast iron or malleable cast iron which consists in welding them together by the passage across the joint of a current of high density for so short a period of time as to avoid solution of any large part of the graphite and subjecting the welded article to a short anneal for as little as about five or ten minutes at an ordinary annealing temperature of about 1450 degrees F.

3. The method of uniting parts of gray cast iron which consists in welding them together by the passage across the joint of a current of high density for so short a time as to retain the graphite in approximately its original quantity and subjecting the welded article to a short anneal for as little as about five or ten minutes at an ordinary annealing temperature of about 1450 degreesF.

\ In witness whereof, I have hereunto signed my name.

- GEORGE H. PHELPS.

. The article thus welded is subjected to a.

short anneal at ordinary temperatures to bring the welds more nearly to theorigina] condition. In any case thejoint will remain somewhat stronger than the rest of the article.-' This is rather an advantage since the malleability permits the article to yield at points outside of the joints and thus to diminish the strain on the joints (where. the external forces tending to breakage are usually greatest).

In all resistance weldingoperations, there.

is a certain dissipation of a; percentage of any carbon present. Such partial dissipation of the carbon occurs also in the operation described herein with gray and malleable cast iron. When I speakof bringing the graphite, by annealing, back to approxi- ,mately its original quantity, allowance must bem'ade for a comparatively small percentage of the original graphite which has been entirely dissipated in the welding operation. 

